Repetitive reentrant and non-reentrant ventriculoatrial synchrony in dual chamber pacing

Endless loop tachycardia among patients with devices having advanced preventive algorithms: A case series and brief review

BACKGROUND

Endless loop tachycardia (ELT) is the commonest pacemaker mediated tachycardia (PMT) encountered among patients with cardiac implantable electronic devices (CIEDs). Despite being enabled with various preventive algorithms, we encountered several cases having recurrent, long, and symptomatic ELT.

MATERIALS AND METHODS

We retrospectively analyzed consecutive device checkups at device clinic at a single center of eastern India between January 2019 to March 2023.

RESULTS

There were 20 cases of confirmed and sustained ELT among 4520 device checks. Although mostly benign, in two cases ELT led to clinical worsening in patients having left ventricular (LV) systolic dysfunction. Even with good ventricular function, ELT resulted in improper atrioventricular (AV) synchrony leading to disabling symptom in one case. The differentiation of ELT from sinus tachycardia and atrial tachycardia (AT) was not always easy. Magnet application is certainly useful to differentiate. The situations that provoked ELT in this study were-long AV delays, VIP (ventricular intrinsic preferences)/MVP (managed ventricular pacing), atrial non-capture, atrial under/over sensing, premature ventricular contractions (PVCs)/couplets, premature atrial contractions (PAC) and slower ventriculo-atrial (VA) conduction. Rate responsive shortening of post-ventricular atrial refractory period (PVARP) also promoted its occurrence and hindered troubleshooting. When ELT occurred despite post-PVC extension of PVARP, lowering the atrial sensitivity, switching to bipolar sensing and manual setting of longer PVARP after measuring VA conduction time were useful. "Rate responsive PVARP" had to be turned off in a few cases to prevent ELT. On the contrary, an over aggressive prolongation of PVARP led to repetitive non-reentrant ventriculo-atrial synchrony (RNRVAS) in two cases. Checking VA conduction during implantation and noninvasive program stimulation (NIPS) during follow up were useful to check the tendency for ELT.

CONCLUSION

Clinically significant ELT is rare but not uncommon among devices having in-built preventive algorithms. Manual adjustments are often useful to troubleshoot the same.

Pseudo repetitive non-reentrant ventriculoatrial synchrony: Current challenges

BACKGROUND

We recently described a novel pacemaker-mediated arrhythmia in Abbott cardiac implantable electronic devices (CIED), called pseudo-RNRVAS, that mimics repetitive non-reentrant ventriculoatrial synchrony (RNRVAS), but can appear in patients with ventriculoatrial (VA) block. It is caused by sinus-p-waves, trapped in the post-ventricular atrial refractory period (PVARP), which mimic VA conduction. The p-waves are followed by atrial pacing during the myocardial refractory time, which can trigger atrial fibrillation (AF). Pseudo-RNRVAS and RNRVAS are probably more common than appreciated, but the recognition and differentiation of the two can be challenging because most CIEDs do not recognize and store them.

OBJECTIVE

We illustrate practical challenges in the assessment of Pseudo-RNRVAS and provide programming options that proved safe and effective for preventing Pseudo-RNRVAS and reducing the risk for typical RNRVAS.

METHODS AND RESULTS

We illustrate in 10 patients the characteristics of Pseudo-RNRVAS and their treatment. The outcome regarding the recurrence of pseudo-RNRVAS after 6 months of follow-up was collected. Inappropriate atrial pacing during pseudo-RNRVAS resulted in AF in six patients. After shortening the PVARP in nine, inactivation/reduction of rate response in four, and reduction of the basic pacing rate in one patient, pseudo-RNRVAS was avoided in eight patients and reduced in one. In one patient AF became permanent.

CONCLUSIONS

Pseudo-RNRVAS is a pacemaker-mediated arrhythmia that can appear in patients without VA conduction and may lead to AF. The suggested adjustments of pacing parameters were safe and effective in preventing the arrhythmia.

Potential triggering of repetitive nonreentrant ventriculoatrial synchrony by loss of atrial capture

BACKGROUND

Data on the factors that trigger repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) are limited. We hypothesize that loss of atrial capture may trigger RNRVAS. We aimed to use an atrial threshold test to observe the development of RNRVAS upon loss of atrial capture in patients with implantable cardiac electronic devices (CIED).

METHODS

Patients with DDD mode CIEDs [177 patients, 67.5 ± 14.8 (70) years; 70 women] were included. Atrial threshold test was done in DDD mode at a rate at least 10 beats above the basal heart rate, with an AV delay of 300 ms (range 250-350). A multivariable logistic regression model was used to assess the independent predictors of RNRVAS.

RESULTS

RNRVAS was observed in 69 of the 177 patients (39.0%) during atrial threshold test. In patients with VA conduction, incidence of RNRVAS increased to 76.7%. In univariate analysis, younger age (p = .038) and the presence of VA conduction (p < .001) were associated with an increased risk of RNRVAS, whereas complete AV block or any AV node conduction defect (p < .001) and the ventricular pacing ratio (p = .001) were inversely related to the risk of RNRVAS occurrence after loss of atrial capture. In multivariate analysis complete AV block (p = .009) and ventricular pacing ratio (p = .029) appeared as independent factors inversely related to the risk of RNRVAS development.

CONCLUSION

In this study, we demonstrated that loss of atrial capture results in RNRVAS in one-third of patients with a CIED in DDD mode, and in three-fourths of those with VA conduction under certain predisposing CIED settings.

A rare case of pacemaker mediated tachycardia caused by intrinsic conduction search function of a dual chamber pacemaker

Pacemaker-mediated tachycardia (PMT) is a well-described cause of tachyarrhythmia in patients with dual chamber pacemakers (Barold, 1991 [1]). PMT is usually caused by common triggers including premature ventricular or atrial complexes (Alasti et al., 2018 [2]). However, PMT can also be triggered by other uncommon mechanisms. Intrinsic conduction search function is a feature available in some dual chamber permanent pacemakers that periodically looks for intrinsic conduction by gradually prolonging the preprogrammed AV delay in an attempt to minimize ventricular pacing (Calvi et al., 2017; Pakarinen and Toivonen, 2013 [3,4]). Here, we report a rare case of PMT triggered by intrinsic conduction search function.

Novel Pacemaker-Mediated Arrhythmia Without Ventriculoatrial Conduction Can Induce Atrial Fibrillation

Cardiovascular implantable electronic devices can initiate and sustain pacemaker-mediated arrhythmias. Endless loop tachycardia and repetitive non-re-entrant ventriculoatrial synchrony (RNRVAS) are well-described examples of pacemaker-mediated arrhythmias. However, such arrhythmias only occur in the presence of ventriculoatrial conduction. We identified a novel pacemaker-mediated arrhythmia that closely mimics RNRVAS but in the absence of ventriculoatrial conduction. We identified these arrhythmias in 9 patients, all with a St. Jude Medical/Abbott device, recorded as inappropriate mode-switch episodes by a device algorithm that includes paced events in the atrial counter. This report describes the mechanism, discusses clinical implications, and outlines programming options to eliminate this pseudo-RNRVAS.

Reversible left ventricular dysfunction due to endless loop tachycardia in patient with dual chamber pacemaker- A case report

A 60 years male patient underwent permanent pacemaker [DDDR -with dual chamber pacing (D) with dual chamber sensing (D) with dual mode of response (D) with rate responsive pacing(R) -St Jude's medical (Abbott- Endurity 2160)] implantation for complete heart block (CHB). After 4 months patient was admitted for congestive heart failure. 12 Lead electrocardiograms (ECG) was suggestive of tachycardia at 130 beats per minute (regular rhythm), with ventricular complexes preceded by pacing spikes and maintenance of 1:1 atrio-ventricular relationship. Echocardiography showed global hypokinesia of left ventricular (LV) myocardium with reduced LV ejection fraction. LV dysfunction and heart failure were attributed to tachy-cardiomyopathy. Pacemaker telemetry data demonstrated that the tachycardia was likely to be pacemaker-mediated endless loop tachycardia (ELT). ELT in this case was perpetuated secondary to shortening of post ventricular atrial refractory period (PVARP), intact retrograde ventriculo-atrial (VA) conduction and addition of antiarrhythmic drugs prolonging retrograde VA conduction. Rate response (Dynamic) PVARP was reprogrammed allowing PVARP extension. Following this ELT was terminated. LV ejection fraction was normalized on subsequent follow up visit after seven days.

Pacemaker-mediated tachycardia in a dual-lead CRT-D: What is the mechanism?

A 73-year-old gentleman with dilated cardiomyopathy, left bundle branch block and a left ventricular (LV) ejection fraction of 20% was implanted with two LV leads in a tri-ventricular cardiac resynchronisation therapy defibrillator (CRT-D) trial. As a part of the trial he was programmed with fusion-based CRT therapy with dual LV lead only pacing. The patient presented to local heart failure service 12 years after implant, after a positive response to CRT therapy, with increase in fatigue, shortness of breath and bilateral pitting oedema. The patient sent a remote monitoring transmission that suggested loss of capture on one of the LV leads. This coupled with atrial ectopics was producing a high burden of pacemaker-mediated tachycardia (PMT) that was not seen when both LV leads had been capturing. What is the mechanism for this? Dual LV-lead tri-ventricular leads have been shown to have variable improvements in CRT response but with an increased complexity of implant procedure. This is the first case report of PMT-induced heart failure exacerbation in a tri-ventricular device following loss of LV capture of one lead.

Is competitive atrial pacing a possible trigger for atrial fibrillation? Observations from the RATE registry

BACKGROUND

A high incidence of asymptomatic atrial tachycardia and atrial fibrillation (AT/AF) has been recognized in patients with cardiac implantable devices (CIED). The clinical significance of these AT/AF episodes remains unclear. Some "device-detected AT/AF" was previously shown to be triggered by competitive atrial pacing (CAP).

OBJECTIVE

To investigate and characterize a potential association between CAP and AT/AF in the largest series of observations to date.

METHODS

RATE, a multicenter registry, included 5379 patients with CIEDs followed for approximately 2 years. Electrograms (EGMs) from 1352 patients with AT/AF, CAP, or both were analyzed by experienced adjudicators to assess a causal relationship between AT/AF and CAP onset, duration, and morphology.

RESULTS

In 225 patients, 1394 episodes of both AT/AF and CAP were present in the same tracing. CAP and AT/AF were strongly associated (P ≤ .02). AT/AF occurred during the course of the study in 71% of patients with CAP. In 62% of the episodes, expert adjudication concluded that CAP triggered AT/AF. The duration and morphology of triggered and spontaneous AT/AF episodes differed. Spontaneous AT/AF episodes were associated with constant EGM morphology, and were either long or extremely short. CAP-triggered AT/AF more often had variable and shorter cycle length EGMs. The incidence of short AT/AF events was higher among triggered episodes (25% vs 12.8%, P < .002).

CONCLUSION

Device-triggered AT/AF due to CAP is likely more common than previously recognized. This AT/AF entity differs from spontaneous AT/AF in duration and morphology. Clinical implications of spontaneous and device-triggered AT/AF may be different.

Proarrhythmic effects from competitive atrial pacing and potential programming solutions

BACKGROUND

Programmed long AV delays and intrinsic long first degree AV block may increase risk for competitive atrial pacing (CAP) in devices without CAP avoidance algorithms.

METHODS

Patients identified with CAP-induced mode switch episodes were followed clinically from September 2013 to August 2019. Attempts to avoid CAP included shortening of postventricular atrial refractory period (PVARP) or postventricular atrial blanking period (PVAB), or change to AAI or DDI modes. After observing associations with sensor-driven pacing, rate response was inactivated in a subset.

RESULTS

Among 23 patients identified with CAP (22 St Jude Medical [Abbott]; one Boston Scientific Corporation devices), atrial fibrillation (AF) was induced in 12 (52%), lasting 10 seconds to 28 hours and 32 minutes. In one patient with an ICD CAP-induced AF with rapid ventricular rates that triggered a shock, inducing ventricular fibrillation, syncope, and another shock. Changing AV delays and shortening of PVARP failed to resolve CAP. After noting that all had CAP during sensor-driven pacing, rate response was inactivated in seven, resolving further device-induced AF in the three of seven that had prior CAP-induced AF. In two patients with intact AV conduction, AAI(R) pacing resolved further documentation of CAP.

CONCLUSIONS

CAP predominantly occurs during sensor-driven atrial pacing that competes with intrinsic atrial events falling in PVARP. Inactivation of the activity sensor or change to atrial-based pacing modes (AAI/R) appears to effectively prevent induction of device-induced atrial proarrhythmia. Ultimately, a corrective algorithm is needed to avoid CAP-induced proarrhythmia.

Pacemaker-mediated arrhythmias

Pacemakers can be directly involved in initiating or sustaining different forms of arrhythmia. These can cause symptoms such as dyspnea, palpitations, and decompensated heart failure. Early detection of these arrhythmias and optimal pacemaker programming is pivotal. The aim of this review article is to summarize the different types of pacemaker-mediated arrhythmias, their predisposing factors, and mechanisms of prevention or termination.

A review of the atrial upper rate algorithms of St. Jude Medical (Abbott) cardiac implantable electronic devices : Incidence of repetitive nonreentrant ventriculoatrial synchrony (RNRVAS)

This review focuses on the manifestations of the three triggered atrial upper rate functions of St Jude Medical cardiac implantable electronic devices. The occurrence of repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) is also evaluated as a basis for the development of automatic mode switching (AMS) and as a trigger for atrial tachycardia/atrial fibrillation (AT/AF) event recordings. RNRVAS is a common trigger for AMS because all the atrial events or intervals are used to calculate the filtered atrial rate interval (FARI). Once AMS is initiated, it will also effectively stop RNRVAS because entry into AMS also shortens the postventricular atrial refractory period (PVARP). Recent design developments to eliminate or minimize unusual upper rare responses include the following: (1) P waves in the PVARP are no longer counted towards the FARI if they are followed by an atrial paced event. (2) In new devices the AT/AF detection algorithm substitutes the Moving Average Interval (a relatively complex calculation) with the new FARI average. (3) Improved design of the rate-responsive PVARP with a far more aggressive response than in the past (enhanced atrial protection interval).

Pacing in sinus node disease to prevent atrial fibrillation

Cardiac pacing is the only effective treatment for patients with symptomatic sinus node disease (SND). The majority of patients with SND have several risk factors associated with development of atrial fibrillation (AF) at the time of pacemaker implantation and are therefore considered a high-risk population. Patients with SND can be treated with any kind of commercially available pacemaker pacing in the atrium, the ventricle or both. Pacing in SND can therefore alter atrial and ventricular conduction and atrioventricular coupling. These mechanisms can prevent or contribute to initiation and maintenance of AF during pacing. Different pacemaker modalities and algorithms have been tested to reduce AF in patients with SND in recent decades. To prevent AF in this population, it seems to be important to mimic the optimal electromechanical function of the heart, especially to preserve an optimal atrioventricular coupling.

[Stored electrograms in pacemakers and ICDs]

Stored electrograms (EGMs) represent an important development in pacemaker and ICD therapy. The most important issue in pacemaker EGMs is the confirmation of the detection of atrial tachyarrhythmias, especially atrial fibrillation. In ICD therapy, the discrimination between ventricular and supraventricular tachycardia (i.e., detection of inadequate therapy) is of central interest. Unfortunately, systematic"instructions" for interpreting stored EGMs in systems by different manufacturers are not available and the knowledge on this topic is limited to (too) few experts. The contributions in this issue aim at explaining the interpretation of stored EGMs in systems by different manufacturers, providing an understanding of marker annotations and EGM registrations in clinical examples. With the aim of improving pacemaker and ICD therapy, a broad distribution of knowledge on the usefulness and the practical use of stored EGMs is highly desirable.

[Stored electrograms in pacemakers and ICDs from St. Jude Medical]

Stored electrograms (EGMs) significantly improve pacemaker and ICD therapy. In pacemaker systems, the main focus of stored EGMs concerns the manual control of device detection of atrial tachyarrhythmias, especially atrial fibrillation. In ICD therapy, stored EGMs allow the discrimination of adequate and inadequate detection of ventricular tachycardia. This review presents the implementation of stored EGMs in systems from St. Jude Medical and explains the mode of EGM storage and marker annotations, which are useful for interpretation of stored EGMs and to understand the way the device interprets the EGM. Clinical examples illustrate appropriate and inappropriate device classifications.

Reduction of right ventricular pacing in patients with sinus node dysfunction using an enhanced search AV algorithm

BACKGROUND

Dual chamber pacing typically results in a high percentage of ventricular pacing. A number of studies have been conducted suggesting detrimental effects of ventricular desynchronization produced by long-term RV pacing. Pacemaker algorithms that extend the AV interval to uncover intrinsic AV conduction have been utilized to reduce ventricular pacing. These algorithms are often limited to AV intervals below 250 ms limiting the ventricular pacing reduction. We hypothesized that by allowing AV intervals to extend beyond 300 ms, a marked reduction in RV pacing can be achieved.

METHODS

A total of 30 patients (17 men, mean age 71 +/- 9) with standard Brady indications, and implanted with a Medtronic Kappa 700 pacemaker, were randomized to 2-week treatments with default Search AV (KSAV) parameters or Enhanced Search AV (ESAV) parameters. The Enhanced Search AV algorithm included the capability for continuous adjustment of AV delays and the ability to auto disable in patients with persistent AV block.

RESULTS

Among patients with intact AV conduction, percent VP was greater in KSAV versus ESAV (70 +/- 40% vs 19 +/- 28%, P < 0.001). In patients with persistent AV block, the algorithm suspended appropriately and there was no significant change in the percent VP between both arms of the study. In 18/22 patients, percent VP was reduced below 40%.

CONCLUSIONS

Substantial reduction in ventricular pacing can be achieved by allowing the AV interval parameters to extend beyond 300 ms using the ESAV algorithm. In patients with AV block, ESAV suspended and patients were paced at their nominal settings.

Effects of cardioactive medications on retrograde conduction: Continuing relevance for current devices

INTRODUCTION

Retroconduction (ventriculo-atrial conduction) remains a problem for patients with implanted cardiac rhythm devices. Pacemaker algorithms can detect and terminate endless loop tachycardia (ELT), but actual prevention of ELT may require anti-arrhythmic drugs (AADs). Similarly, AADs can affect ICD rhythm discrimination algorithms that depend on atrio-ventricular ratios. There is concern whether these drugs remain effective during stress situations.

METHODS

Electrophysiologic studies that included retroconduction testing using slow ramp pacing were done in 1332 patients. The presence or absence of retroconduction at baseline and with drug was recorded, as was the rate at block. As a stress surrogate, isoproterenol was used to test retroconduction and reversal of drug-induced block.

RESULTS

Procainamide, mexiletine, phenytoin, disopyramide, quinidine, beta-blockers, encainide, and amiodarone caused complete retrograde block or decreased the rate at which block occurred (mean 76% of patients, p < 0.008), whereas digoxin, lidocaine, diltiazem, and verapamil did not. Isoproterenol (in the absence of AADs) increased the rate at block in 82% of 404 patients with retroconduction at baseline (p < 0.005). Of 319 patients without retroconduction at baseline, 134 (42%) developed retroconduction after isoproterenol. Isoproterenol reversed retrograde block in 39% of patients with block on an AAD. Amiodarone, digoxin, and the combination of digoxin plus a beta-blocker were most effective at resisting this reversal of ventriculo-atrial block (80%, 68%, and 75% respectively).

CONCLUSION

Most of the AADs reviewed increase the cycle length at block or abolish retroconduction, while isoproterenol has the opposite effect. Anti-arrhythmic medications, particularly amiodarone, digoxin, and the combination of digoxin plus a beta-blocker may be considered for a patient with multiple ELT episodes or certain ICD detection problems.

Apropos "Tachycardia Begets Tachycardia"

It has been shown that a tachycardia can facilitate the induction of the same ("atrial fibrillation begets atrial fibrillation") or a different tachycardia. This may also apply for pacemaker-mediated tachycardia as the present case documents.

The pacemaker syndrome -- a matter of definition

Pacemaker syndrome is an iatrogenic disease that is often underdiagnosed. We propose that pacemaker syndrome represents the clinical consequences of suboptimal atrioventricular (AV) synchrony or AV dyssynchrony, regardless of the pacing mode. Clinicians implanting and programming pacemakers should attempt to optimize AV synchrony to prevent the occurrence of pacemaker syndrome.

AAI pacing mode: when is it indicated and how should it be achieved?

AAI pacing offers better hemodynamic characteristics than dual-chamber pacing and is the optimal mode for patients with sick sinus syndrome without AV conduction disorders. AAI pacing may be achieved by single-chamber atrial pacing, by programming a dual-chamber pacemaker to the AAI mode, or by programming a dual-chamber pacemaker to DDD mode with a long AV delay. The annual incidence of AV block development in patients with sick sinus syndrome is low, probably 1-5%, but there is no method of detecting patients immune or prone to future development of AV block. Chronotropic incompetence is often present in patients with sick sinus syndrome but the value of additional rate response is not yet firmly established. Our recommendations for the choice of the optimal method of pacing are discussed.